When building either a communications system or, for instance, a jamming system, it is important that a particular pattern of RF energy be transmitted and that this transmission be made to occur at a precise time. The signals to be transmitted are usually reconstructed from an original signal after the original signal has been processed. Whether the transmission contains analog or digital information, it is important that the reconstructed signal be transmitted at a particular point in time.
This is especially true in communications systems such as time division multiple access systems, in which data is allocated to particular timeslots. In the past, in order to make sure that the data is transmitted exactly at the particular instant of time necessary to place the necessary data in a particular timeslot, the entire transmitting system or indeed, for instance, the entire radio must have timing for each of its parts which is sufficiently accurate so that the signals are in fact transmitted at the appropriate time instant.
This means that assuming, for instance, information is coming in which is converted from analog to digital by an analog-to-digital converter, and further assuming, for instance, that digital processing is used to further process the digitized original signal, and even further assuming that the output of the digital processing is coupled with a digital-to-analog converter coupled to a transmitter, then it will be appreciated that if the transmission is to occur at a precise instant in time, the timing associated with all of the above components must be exceedingly accurate. Thus the problem is that there must be real time processing throughout all of the components used in generating the signal. This requires knowledge of any latency characteristics or delays, along with the provision of an exceedingly accurate timing standard for each one of the components. Note that for purposes of the present invention realtime means better accuracy than that available from standard off-the-shelf products, for instance, nanosecond accuracy.
Achieving such realtime accuracy is an expensive costly process involving specialized hardware that is developed for each and every application.
The result is whether one is dealing with communications equipment or, for instance, jamming systems in which jamming pulses must be emitted with a particular signature at a particular instant of time, in the past the elements themselves making up the entire system must have their timing so carefully constrained and controlled that timing errors are reduced to nanoseconds. It is thus only with difficulty with commercial off-the-shelf products that one can arrange for this type of accuracy.
For instance, if a general-purpose digital processing circuit is used to in any way alter or process an input signal, about the best accuracy commonly available with standard clocks is millisecond accuracy. The dominant source of timing error thus resides in the digital processing circuitry, with millisecond accuracies being insufficient for many applications. The result is that common digital processing units such as general-purpose processors do not provide for the transmission of signals at the precise point in time required. While general purpose processors are in fact quite common and inexpensive, these processors cannot without massive specialized reconfiguration be used to create accurately timed transmissions.
In short, the problem in the past is that the elements making up the communications system must themselves be controlled to nanosecond accuracies to provide the real time result.